Surface abrading machines are known such as are illustrated in German Patents DE19548932 and DE4142396 and which uses chains to impact surfaces of concrete blocks. These abrading devices use a motor driven shaft about which chain links are secured and rotated for impacting a top surface of blocks, which are conveyed thereunder on a conveyor platform. U.S. Pat. No. 6,109,906 discloses a different type of machine and wherein blocks are retained between opposed conveyor belts to each side of a similar abrading device but supported vertically for impacting a surface of each of the blocks conveyed thereby. In all of these devices the blocks need to be reconveyed in order to expose further surfaces as these machines are capable of abrading a single surface only of these blocks. This is an expensive and time-consuming operation. Also, these abrading machines only abrade surfaces of blocks and do not impact on corner areas of the blocks. They were conceived primarily to abrade a surface, which is intended to be exposed to give it the look of an aged stone.